Although silver metal in itself does not exert antimicrobial effect, a majority of silver compounds possess antimicrobial property. Empirically, the Romans in Europe and Indians in Asia have used this knowledge for centuries. In ancient Rome it was common practice to add silver coins to large cisterns of water to improve potability. And in India, the practices of storing clarified fats in silver vessels to prevent rancidity and of applying thin silver foil to sweets are still widespread. The thin foil silver surface protects the sweets from bacteria shed by house flies which are common in sweet shops in tropical India. The antimicrobial or bacteriostatic action in the use of silver coins or foil is due to minute quantity of ionic silver released from the oxidized layer on the silver surface, an effect known as oligo-dynamic action.
In modern medicine, towards the turn of 20th century eye drops consisting of 1% silver nitrate solution were first employed to prevent blindness in newborns delivered by mothers suffering from sexually transmitted diseases. However, despite the tremendous potential of silver compounds as antimicrobials, commercial antimicrobial products that include silver have failed to materialize for several reasons. First, silver compounds containing products tend to degrade with time due to their photo-sensitive nature. This property of silver compounds also makes them thermally sensitive which in turn makes manufacturing products that include silver compounds very challenging. More often than not manufacturing processes involved are energetically very intensive. Second, more robust alternative to silver compounds in the form of antibiotics and other chemical based antimicrobials (xylenol derivatives and biguanides) were developed and have dominated the medical industry for over past fifty years or so. Nonetheless, despite the general limitations of silver compounds, several robust silver based technologies e.g. silver sulfadiazine, stabilized silver chloride, silver saccharinate, silver zeolites and silver zirconium phosphate have found applications in niche areas such as advanced wound care.
These silver technologies however, have their own limitations. For instance, silver sulfadiazine is practically insoluble in water. So, on w/w basis much higher content of the compound is required to exert therapeutically effective antimicrobial effect. And there have been reports of issues related to patient sensitivity to sulfonamides. Silver zeolites and silver zirconium phosphate due to their inorganic nature are unsuitable for inclusion in medical products that require implantation or contact with breached skin. Despite its promise, very few products based on silver saccharinate have been introduced in commerce.
Thus, there is a need for novel antimicrobial silver compounds or a group of silver compounds that form the basis of robust and effective antimicrobial silver technology that can overcome aforementioned limitations. More recently, a novel silver based technology including a group of silver cyanurate compounds was disclosed by the present inventor in the PCT/US2014/035945 application which is hereby incorporated in its entirety by reference for all purposes. The present invention expands upon that development and provides a new class of antimicrobial silver s-triazine compounds that may possess good light and heat resistance and may be readily incorporated in a variety of compositions and devices in both medical and non-medical settings. The said antimicrobial silver s-triazine compounds may possess broad spectrum antimicrobial activity against bacteria, yeast, fungi, viruses and other microorganisms.